Power entry unit electrical power distribution method

ABSTRACT

An electrical power system including a first power entry unit, at least one receptacle, and a second power entry unit. The at least one receptacle is electrically connected to the first power entry unit. The second power entry unit is electrically connectable to the at least one receptacle. The first power entry unit and the second power entry unit include at least one detection device. Either the first power entry unit or the second power entry unit is a selected power entry unit and the remaining one is another power entry unit. The detection device is configured to preclude an electrical power connection of both the selected power entry unit and the other power entry unit to the at least one receptacle.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electrical power supply system, and,more particularly, to an electrical power supply system, which detectsmore than one power source being connected to an electrical receptacle.

2. Description of the Related Art

Electrical wiring codes limit the number of receptacles which can beconnected to a power entry unit. It is common for an electrical powersource to be routed to an electrical receptacle and power then routedfrom that electrical receptacle to subsequent electrical receptacles ina daisy-chaining manner. Although the electrical wiring has theelectrical receptacles connected in parallel, there is no physicallimitation in the wiring to prevent the connection of further electricalreceptacles without limit nor is there anything in the daisy-chaining ofelectrical outlets that precludes the chain of electrical outlets to beconnected to more than one power source.

If a chain of electrical outlets are connected to two power sources,which happens to be of the same voltage and phase and the unitsfunction, a problem can arise in which maintenance personnel maydisconnect a power source only to find out that the receptacles arestill electrically energized.

Another problem can arise in which in the sequential connection ofreceptacles a second power source having a different voltage or phaserelationship than the one connected at the other end of the chain ofreceptacles, thereby causing an immediate electrical issue with twovoltage sources competing to supply power, which will most likely resultin circuits being disconnected by circuit breakers, but generally onlyafter exhibiting some electrical sparking or discharge. This can resultin, at the very least, surprise to the maintenance personnel but alsopotential damage to the wiring and to the equipment attached thereto.

What is needed in the art is a system that will preclude the applicationof electrical power to each end of a chain of electrical receptacles.

SUMMARY OF THE INVENTION

The present invention provides an electrical power system that may beused, for example, in a modular office wall panel system.

The invention comprises, in one form thereof, a modular office systemincluding at least one wall panel having a raceway and an electricalpower system at least partially contained in the raceway. The electricalpower system includes a first power entry unit, at least one receptacle,and a second power entry unit. The at least one receptacle iselectrically connected to the first power entry unit. The second powerentry unit is electrically connectable to the at least one receptacle.The first power entry unit and the second power entry unit include atleast one detection device. Either the first power entry unit or thesecond power entry unit is a selected power entry unit and the remainingone is another power entry unit. The detection device is configured todetect an attempted electrical power connection of both the selectedpower entry unit and the other power entry unit to the at least onereceptacle.

The present invention comprises, in another form thereof, an electricalpower distribution method including the steps of connecting a firstpower entry unit to an electrical receptacle and another step ofdetecting a second power entry unit that is electrically connected tothe electrical receptacle prior to the first power entry unit engagingelectrical power to the electrical receptacle.

The present invention advantageously allows an installer to connectelectrical receptacles in a sequential or non-sequential manner.

Another advantage is that only one type of interconnecting cable isnecessary to connect the electrical receptacles.

A further advantage of the present invention is that each of thereceptacles can be identical.

Yet still a further advantage of the present invention is that more thanone power entry unit is connected to the electrical receptacles. Atleast one of the power entry units will not supply power to thereceptacles.

Yet another advantage of the present invention is that compliance withelectrical code concerns is carried out by the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent and theinvention will be better understood by reference to the followingdescription of an embodiment of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a perspective view of an embodiment of a modular office systemhaving a wall panel with electrical receptacles positioned in a raceway;

FIG. 2 is a schematic block diagram of an embodiment of the electricalpower system used in the modular wall panel of FIG. 1;

FIG. 3 is a schematic block diagram illustrating the connection of apower entry unit used in the power supply system of FIGS. 1 and 2connected to a series of receptacles;

FIG. 4 is another block diagram illustrating the connection of a seriesof receptacles and more than one power entry unit; and

FIG. 5 is a state diagram illustrating the functions of the presentinvention of FIGS. 1-4.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate one embodiment of the invention and such exemplifications arenot to be construed as limiting the scope of the invention in anymanner.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and more particularly to FIG. 1, there isshown a modular office system 10 including a modular wall panel 12, araceway 14, and electrical receptacles 16. Modular office system 10 isutilized in an office space as partitioning walls in an open floor planenvironment.

Now, additionally referring to FIG. 2, there is shown electrical powersystem 18 that includes receptacle 16 connected by way of amulticonductor cable 20 to a power entry unit 22. Power entry unit 22includes an input connector 24, a power switching device 26, a powersupply 28, a detection device 30, feedback indicators 32, sensors 34,and an output connector 36. Input connector 24 may be a three wireconnector that contains a line, neutral, and ground, and may be rated at120 volts AC. Input connector 24 is electrically connectable to areceptacle or other electrical power source.

Input connector 24 supplies electrical power to power supply 28 and topower switching device 26. Power switching device 26 may be in the formof electrical relay 26 or a noncontact switching relay 26. Power supply28 includes circuit protection elements to protect power supply 28.Power supply 28 provides power to detection device 30.

Detection device 30 may be implemented with logic devices, analogdevices, and/or software to carry out its protection functions.Detection device 30 controls the power supplied to relay 26 and decideswhen relay 26 should be energized to thereby pass electrical powertherethrough to output connector 36. Detection device 30 additionallyprovides feedback to a user by way of feedback indicators 32, which maybe in the form of LEDs 32 to indicate the status of power entry unit 22.Detection device 30 communicates to sensors 34, which detect both thenumber of receptacles 16 connected to power entry unit 22 and alsosenses the attempted electrical connection of another power entry unit.Output connector 36 has exterior electrical connections so that cable 22can pass power onto receptacles 16. Additionally, output connector 36may be configured to supply power on some electrical connections andalso pass other signals by way of other communication devices, such asoptical or other communication methods. For purposes of explaining thepresent invention, electrical connections to output connector 36 willinclude line, neutral, ground, and a signal line capable of passingsignals, which may be in the form of voltage levels that are altered bythe connection of additional receptacles 16.

Power supply 28 creates a logic level DC voltage from the line voltageprovided by way of input connector 24. This logic level DC voltage maybe 5 volts DC. Detection device 30 incorporates the logical constructsand devices used to control relay 26 and to receive information fromsensors 34. Detection device 30 senses the number of receptacles 16present by measuring the voltage on the signal line by way of ananalog/digital input therein. Sensors 34 interact with detection device30 to pass a set amount of current down the sensor lines that areelectrically connected to receptacle 16, which cause the voltage sensedby sensors 34 to fall or rise as receptacles are added or removed. Ifthe resulting value of voltage is greater than a predeterminedthreshold, it is determined that eight or fewer receptacles areconnected to power entry unit 22 and relay 26 can remain on, or isturned on after an initial power up mode. If the resulting value is lessthan or equal to the predetermined value of voltage, then it isdetermined that nine or more receptacles are connected and relay 26 isturned off, thereby de-energizing receptacles 16.

Detection device 30, along with sensors 34, additionally sense if morethan one power entry unit is connected to receptacles 16. In oneembodiment, detection device 30 utilizes a random or pseudo-randomnumber generator that periodically stops driving current out of thesensor line going to receptacles 16. If another power entry unit isconnected, it will still be driving current into the sensor lines and avoltage will be measured when none is expected. This causes detectiondevice 30 to conclude that another power entry unit is electricallyconnected to receptacle 16. Relay 26 remains off until the situation iscorrected and may additionally remain off until power is removed frominput connector 24 and reapplied. The random number generator thatdetermines the periodicity of the check of the sensor line is such thatwhen an additional power entry unit is trying to check the samesituation, then the units will not be trying to perform the sensing ofeach other at the same time, which would result in the units not sensingeach other. It is also contemplated that the sensing operation may bepreformed multiple times at random intervals of time, before concludingthat relay 26 can be energized.

LED's 32 may be a red/green bicolored LED used as a feedback indicator32. A solid green light is illuminated when relay 26 is engaged and onlyone power entry and eight or fewer receptacles are connected to powerentry 22. A blinking red indication on LED 32 indicates that one powerentry and nine or more receptacles are connected. A solid red indicationby LED 32 indicates the detection of two or more power entry unitsconnected to receptacles 16.

Sensor 34 perform two separate, independent functions in that they sensethe number of receptacles 16 connected to electrical power system 18 andsense if one or more power entries are also connected thereto.

Receptacles 16 are standard three prong outlet receptacles containing aline output, which is switched by power relay 26, a neutral, and aground. There is also a wire that is connected to a device that issensed by sensors 34. A device that is detected within receptacle 16 maybe a resistor, the presence of which is detected by a change in voltageas additional receptacles 16 are connected thereto. Alternatively, thedevice in receptacle 16 may be some other electrical device, such as acapacitor, inductor, or logic element, for example. The device thenloads or alters the signal sent on the sensor line so that detectiondevice 30 can determine the number of receptacles 16 are connected topower entry unit 22. Additionally, the device can be an optical elementor some other element that provides information over the lines connectedby way of cable 20 so that detection device 30 may detect the additionalconnection of receptacles 16.

Now, additionally referring to FIG. 3, there is illustrated a powerentry unit 22 connected to receptacle 16-1 through 16-N. When the numberof receptacles exceed a predetermined number, such as eight, then powerentry unit 22 takes action, which may include a visual indicator by wayof LED 32 and/or the disconnection of power to receptacles 16-1 though16-N by the de-energizing of relay 26.

Now, additionally referring to FIG. 4 where a number of receptaclesincluding 16-1, 16-N, 16-N+1, and 16-Z are physically connected to apower entry unit 22 and an additional power entry unit 122. Power entryunit 122 is substantially similar to power entry unit 22 in that sensorlines are connected therebetween by way of cables 20. Although FIG. 4denotes a sequential connection of receptacles between power entry unit22 and power entry unit 122, it is also to be understood thatreceptacles could branch off therefrom and that the electricalconnection is still an electrical parallel connection. So whether theyare depicted in a sequential linear arrangement such as in FIG. 4 orbranched off in other physical configurations, electrically, receptacles16-1 through 16-Z are electrically connected in parallel.

Power entry unit 22 and power entry unit 122 are physically connected.When power is supplied to both power entry unit 22 and power entry unit122 before the relay 26 in each power entry unit is energized, thepresent invention carries out a sequence of steps to preclude electricalpower from being applied by both power entry unit 22 and power entryunit 122. The present invention carries out its function in that each ofthe power entry units detect the presence of each other by way of theelectrical signals on the signal line so that electrical power is notconnected to the line of receptacles 16 by either of the power entryunits.

Now, additionally referring to FIG. 5, there is illustrated a statediagram 50 of electrical power system 18. State 52 is entered when poweris supplied to a power entry unit. At that point, relay 26 is off andLED 32 is solid red. If power entry unit 22 detects that it is the onlypower entry unit and that between zero and eight receptacles areelectrically connected thereto, then power entry unit 22 proceeds tostate 56, where relay 26 is activated, LED 32 is changed to solid greenand receptacles 16 are electrically energized. This is the normaloperating condition of power entry unit 22; however, it continuouslychecks to determine if too many receptacles 16 are connected thereto orif an additional power entry unit is connected to the receptaclesconnected to power entry unit 22. While in state 56, if an additionalpower entry unit is detected, then power entry unit 22 transitions tostate 52 with relay 26 being de-energized and LED 32 being changed to asolid red color. Additionally, when in state 56, if nine or morereceptacles are detected, then power entry unit 22 transitions to state54 where relay 26 is de-energized and LED 32 will blink red.

While power entry unit 22 is in state 54, if it detects that the numberof receptacles have been reduced to eight or fewer and that there isonly one power entry unit, then power entry unit 22 transitions to state56, relay 26 is energized, and LED 32 is illuminated as solid green. Ifwhile in state 54 two or more power entry units are detected, then powerentry unit 22 transitions to state 52 where relay 26 remains off and LED32 is illuminated as solid red. If while in state 52 power entry unit 22detects the reduction to one power entry unit and yet nine or morereceptacles, then power entry unit 22 transitions to state 54 whererelay 26 remains de-energized and LED 32 blinks red. Also, while instate 52 as long as two or more power entry units are detected thenpower entry unit 22 remains in state 52. Also, as previously noted, ifwhile in state 52 one power entry unit and eight or fewer receptaclesare detected, then power entry unit transitions from state 52 to state56.

Each receptacle 16 as well as each power entry unit may have an internalresistor of 1,000 ohms between the signal line and ground. Connectingmultiple receptacles together therefore also connects multiple 1Kresistors together in parallel. Detector 30 may utilize the parallelresistor formula to determine the number of receptacles connected topower entry unit 22 since (1/R)=R1+1/R2+ . . . 1/Rn. The totalresistance between the signal line and ground can be calculated based onthe number of receptacles connected. This total resistance is theresistance seen by the power entry module. The power entry moduleprovides a constant current of, for example, 15 mA through this totalresistance. In this manner, the number of receptacles can be calculatedby detector 30 and, upon exceeding a predetermined number, such aseight, it may de-energize relay 26. However, if the measured voltage isbelow the threshold, there are more than eight receptacles and detector30 will de-energize relay 26. The sensing of the number of receptaclesconnected to a power entry unit may be temporarily suspended when powerentry unit 22 attempts to detect the connection of an additional powerentry unit.

Another method of detecting a power entry unit includes each power entryunit monitoring the voltage on the signal line as explained above. Eachof the power entry units will randomly or pseudo-randomly short thesignal line to ground causing the second power entry module to see thesignal line voltage as zero volts and turn off its relay 26. Thisshorting to ground of the signal line in a random manner avoids powerentry units from every synching together and not detecting each other.The pseudo-random or random number generator can be considered an eventgenerator that selects a time in which to alter the detection signalsent from the power entry unit to thereby enable the detection device 30to sense detection signal being sent from another power entry unit. Theconcept of attempted electrical power connection should be understood tomean that the actual electrical power is not connected if either thepower entry unit detects another power entry unit or if too manyelectrical receptacles are connected to the power entry unit. It is tobe understood that the power entry unit is physically connected but theactual electrical power distribution is held in abeyance until the powerentry units are correctly configured to only supply separate sets ofelectrical receptacles.

The present invention advantageously precludes the erroneousinterconnection of multiple electrical power entry units andadditionally precludes the connection of too many receptacles to asingle power entry unit.

While this invention has been described with respect to at least oneembodiment, the present invention can be further modified within thespirit and scope of this disclosure. This application is thereforeintended to cover any variations, uses, or adaptations of the inventionusing its general principles. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which this invention pertains andwhich fall within the limits of the appended claims.

1. An electrical power distribution method, comprising the steps of:connecting a first power entry unit to at least one electricalreceptacle; connecting a second power entry unit to at least oneelectrical receptacle; and precluding an application of electrical powerto said at least one electrical receptacle when electrical power issupplied to both said first power entry unit and said second power entryunit.
 2. The method of claim 1, further comprising the step of engagingelectrical power to said at least one electrical receptacle whenelectrical power is supplied to only one of said first power entry unitand said second power entry unit.
 3. The method of claim 1, furthercomprising the step of altering an illumination of an indicatordependent upon electrical power being supplied to both of said firstpower entry unit and said second power entry unit.
 4. The method ofclaim 1, further comprising the step of selecting a time and at saidtime altering a detection signal sent from said first power entry unitthereby enabling said first power entry unit to sense a detection signalbeing sent from said second power entry unit to thereby detect theattempted electrical power connection of said first power entry unit tosaid at least one electrical receptacle.